The present invention relates to equipment for changing a blade in a coating device, in which the blade is intended to be used in connection with coating, in a blade holder fitted to a blade beam, and in which the blade is formed as an elongated flexible band, the coating device including                a blade-beam suspension arranged in connection with the frame at the ends of the blade beam, and which is arranged in a hollow shaft fitted to the frame, in such a way that, in the running position, the central axis of the hollow shaft is arranged to lie essentially on the edge line of the blade, and        control equipment, arranged in connection with the blade-beam suspension, for adjusting the blade angle during running.The invention also relates to a method for changing a blade in a coating device and a blade for use in a coating device.        
Blades intended for coating are used in on-line coating stations in connection with paper and board machines, and in so-called off-line coating devices, which in terms of production are separate from the actual paper machine. Both of these will be referred to in the following by the general term coating device. In blade coating, the blade is used to regulate, among other things, the amount of coating remaining on the paper and to smooth the coated surface.
In coating, the blade wears in a very short time, causing it to lose the properties required for a successful coating result. Due to this, the blade must be changed for a new one on average at intervals of 4 to 8 hours running time. In addition, the blade is changed, for example, during web breaks and shutdowns, whether it is worn or not. Traditionally, blades in coating devices have been changed manually by the operators. However, it is difficult and even dangerous to change long blades. In addition, the regular changing of blades takes up a great deal of useful production time, leading to production losses. Further, during blade changing, uncoated broke is created, especially in situations in which coating takes place as an on-line operation in connection with the paper machine. In that case, the paper machine is run at the running speed set for it, even while the blade is being changed. Besides reducing effective production time, blade changes also tie up labor.
Finnish patent number 103596 discloses a changing equipment for a doctor blade. In the equipment, a band-like blade is fed to a blade holder from a reel and is then pulled from the blade holder onto a second reel. During changing, a band containing several blades can then be simply fed with the aid of operating devices.
However, in known types of coating devices, structural factors make the equipment described above unsuitable for changing coating blades. In a coating device, the blade holder is, as is known, arranged in a blade beam, the width of which corresponds at least to that of the backing roll. In the coating situation, the blade is loaded against the backing roll, the paper web, to which coating paste has been applied, running between the edge line of the blade and the backing roll. The blade beam is suspended on bearings from both sides of the coating device, in a so-called rotating frame. There is an opening in the upper part of the frames, in which there is a hollow shaft that acts as the bearing point for the blade beam. During running, the blade angle is adjusted by rotating the blade beam.
When the blade is changed, it can be brought into contact with the opened blade holder, for example, through the hollow shaft. The imaginary center-line of the hollow shaft in the running position is essentially at the line of the edge of the blade. This means that the lower edge of the gap formed by the locking jaws of the blade holder, against which the side of the blade opposite to the edge line is set when the blade is in the holder, is radially outside an imagined extension of the hollow shaft. Due to this, among other factors, known types of blade-changing equipment are in no way suitable for use in coating devices.
In addition, it would also be difficult to feed the band using known types of equipment, as in reality there is generally little installation space in connection with coating devices. Thus the reels would have to be located far from the coating device, in which case the band would have to be guided using complicated guide devices.